Tropical Storm Debby has formed in the Gulf of Mexico

Tropical Storm Debby has been named by the National Hurricane Center this afternoon after hurricane hunters investigated Invest 96L and found a solid closed circulation, with maximum winds of 50mph and gusts up to 65mph. All interests along the Gulf of Mexico coast should pay attention to the progress of Debby. Debby is drifting north at 5mph. The storm has brought heavy rains to Western Cuba, South Florida, and Mexico's Yucatan Peninsula over the past two days, but the disturbance's heaviest rains are located well offshore over the Eastern Gulf of Mexico, where heavy thunderstorms are generating winds near tropical storm-force. A buoy 243 miles west of Naples, FL measured sustained winds of 31 mph, gusting to 38 mph, with 10-foot waves, at 8 am EDT Saturday morning. Our Wundermap for the surrounding ocean areas shows a large region of the northern and eastern Gulf of Mexico is experiencing winds of 20 - 30 mph.

Visible satellite loops show an unorganized tropical cyclone with an obvious surface circulation, though the thunderstorm activity is well displaced to the east. The heavy thunderstorm activity is slowly expanding and growing more intense. Upper-level winds out of the west continue to create moderate 10 - 20 knots of wind shear over the region, though that is expected to increase over the next few days. Water vapor satellite loops show a region of dry air over the central Gulf of Mexico, which will continue to interfere with Debby's development and make it hard for the west side of the circulation to maintain heavy thunderstorms. Ocean temperatures are about 28.5°C (83°F) in the Central Gulf of Mexico, which is about 1°F above average.

Forecast for DebbyThe National Hurricane Center is forecasting Debby to remain a tropical cyclone over the next 5 days as it drifts north and then west toward Texas. The Hurricane Center is forecasting a very slow progression of the storm, with a potential landfall not occurring until Friday. However, most of the models that predict the turn to the west suggest landfall will happen before or around Wednesday. The models are still generally split on the forecast for Debby; by Monday, the majority of the reliable models, including the ECMWF, NOGAPS, HWRF, and UKMET, agree that a ridge of high pressure will build in over the Southern U.S., forcing Debby west across the Gulf of Mexico and into South Texas by Wednesday. However, the GFS model, which has been our 2nd most reliable track model over the past two years (behind the ECMWF), has consistently been predicting that a trough of low pressure pushing off of the U.S. East Coast will be capable of grabbing the disturbance and accelerating it to the northeast across Florida north of Tampa Bay on Monday. The GFDL model splits the difference between these extremes and takes Debby north to a landfall near the Alabama/Florida border on Tuesday. The predicted track west to Texas is still the most likely outcome, though it remains a low-confidence forecast. In terms of intensity, none of the models is predicting Debby will become a hurricane, nor is the Hurricane Center. Though sea surface temperature is warm (and around 1°F above average), the actual heat content of the Gulf is relatively low. Wind shear is predicted to remain moderately strong through Sunday, but will increase to 30+ knots by Tuesday.

Debby's place in history (by Jeff Masters)Remarkably, Debby's formation on June 23 comes a full two months ahead of the usual formation date of the season's fourth storm in the Atlantic, August 23. Debby's formation beats by twelve days the previous record for formation of the fourth named storm of the year in the Atlantic, set in 2005, when Hurricane Dennis was named on July 5. An early start to the Atlantic hurricane season has been increasingly common in recent years. In 2008, I blogged about the research of Dr. Jim Kossin of the University of Wisconsin, who published a 2008 paper in Geophysical Research Letters, titled "Is the North Atlantic hurricane season getting longer?" He concluded that yes, there is a "apparent tendency toward more common early- and late-season storms that correlates with warming Sea Surface Temperature but the uncertainty in these relationships is high". Three out of four of this year's early quartet of storms--Alberto, Beryl, and Debby--formed in ocean areas that were more than 1°F above average, which is an unusually high amount of warmth. We should expect to see more early-season Atlantic tropical storms as a consequence of global warming, since cool ocean temperatures are a key impediment to formation of such storms. However, this assumes that factors such as wind shear and atmospheric stability won't grow more hostile for tropical cyclone formation during the early part of hurricane season, and this is uncertain. If we do end up seeing a substantial increase in early-season tropical storms as a consequence of global warming, this is not necessarily a bad thing. Early-season tropical storms are often more boon than bane, bringing much-needed drought-busting rains, like Tropical Storm Beryl did for North Florida last month. With drought frequency and intensity predicted to increase for much of the Gulf Coastal states in coming decades, an increase in rainfall from early-season tropical storms may do more good than the damages inflicted by the high winds and flooding these storms may bring. There is typically a lot of wind shear around in May, June, and July, making it difficult for early season storms to reach major hurricane status. According to Wunderground's list of major early-season hurricanes, since record keeping began in 1851, there has been only one major hurricane in May, two in June, and nine in July. Three of these occurred in the past ten years, so there has not as yet been a large increase in early-season major hurricanes due to global warming.

The convective pattern both in intensity and spatial organization is consistent with the GFS depiction and unlike the ECMWF depiction of a straight band of convection that does not extend into Florida at this forecast hour. If the GFS doesn't win out on track it certainly has done a good job with the precipitation fields.

tommarow morn will tell the truth .when the next hurricane hunter goes out they will have to travel farther north and east to find center, lol. the storm was pointing yesterday ,but no one else was watching . well the GFS was .he he

Quoting Drakoen:The latest ASCAT places Debby farther north and east of the NHC estimate.

Looks like the NHC saw that one coming.ALTHOUGH THERE MAY BE SOME SLIGHTNORTHEASTWARD MOTION DUE TO REDEVELOPMENT OF THE CENTER CLOSER TOTHE DEEP CONVECTION...THE GENERAL MOTION FOR THE NEXT 24 HOURS ORSO SHOULD BE SLOWLY POLEWARD.

The cooling of cloud tops over the past few hours has been rather impressive; additionally, upper-level winds have subsided to about 15-20kts since this afternoon so that's also helping the cause. If the circulation can manage to tuck itself under the coldest cloud tops and continue to fire intense convection, a 20kt intensification isn't all that unlikely within 12 hours.

Debby's center still appears to be slightly west of 87 W. Should that convection continue to blossom, however, it will likely begin to cover the circulation...and intensification would follow. I actually think Debby may be a bit stronger than 50 mph right now. Morning recon flight will be mighty interesting, especially if Debby continues what it is doing now.

As far as satellite appearance, it has improved significantly over the past few hours so if she's intensifying at a good clip it wouldn't come as a surprise. I'd say we'll have a hurricane by late morning should the current trend continue.

As far as satellite appearance, it has improved significantly over the past few hours so if she's intensifying at a good clip it wouldn't come as a surprise. I'd say we'll have a hurricane by late morning should the current trend continue.

Evening guys! Based on the pressure drop to 998 as of the last advisory an increase in winds is sure to follow. Definitely looking more healthy too....convection building further west and even close if not over the center. Those are signs that shear is surely slackening. I'm expecting a 60 mph storm by 2am if not, 5am.

Another thing... Florida's really getting whacked tonight, especially on the west coast. Don't need to be near the center to get some nasty weather!

Quoting TampaSpin:Whats the general rule for storms...the stronger the storm the more poleward pull....a stronger storm would act more like the GFS while a weak system that we currently have would tend to move West toward Texas. Its all going to depend on where she goes based on her strength at this point IMO!

Hey Tampa...thanks for your input. I have always liked your explanations. I hope you all aren't getting too much rain over there.